Abstract. Measuring air pressure using a capacitive pressure sensor is a robust and precise technique. In addition, a system that employs such transducers lies within the low power consumption applications such as wireless sensor nodes. In this article a high sensitivity with an elliptical diaphragm capacitive pressure sensor is proposed. This design was compared with a circular diaphragm in terms of thermal stresses and pressure and temperature sensitivity. The proposed sensor is targeted for tyre pressure monitoring system application. Altering the overlapping area between the capacitor plates by decreasing the effective capacitance area to improve the overall sensitivity of the sensor ( C/C), temperature sensitivity, and built-up stresses is also examined in this article. Theoretical analysis and finite element analysis (FEA) were employed to study pressure and temperature effects on the behaviour of the proposed capacitive pressure sensor. A MEMS (micro electro-mechanical systems) manufacturing processing plan for the proposed capacitive sensor is presented. An extra-low power short-range wireless read-out circuit suited for energy harvesting purposes is presented in this article. The developed read-out circuitry was tested in terms of sensitivity and transmission range.

The safety of the driving experience and manoeuvrability of a vehicle can be improved by detecting the strain in tyres. To measure strain accurately in rubber, the strain sensor needs to be flexible so that it does not deform the medium that it is measuring. In this work, a novel flexible bond wire capacitive strain sensor for measuring the strain in tyres is developed, fabricated and calibrated. An array of 25 micron diameter wire bonds in an approximately 8 mm × 8 mm area is built to create an interdigitated structure, which consists of 50 wire loops resulting in 49 capacitor pairs in parallel. Laser machining was used to pattern copper on a flexible printed circuit board PCB to make the bond pads for the wire attachment. The wire array was finally packaged and embedded in polydimethylsiloxane (PDMS), which acts as the structural material that is strained. The capacitance of the device is in a linear like relationship with respect to the strain, which can measure the strain up to at least ±60,000 micro-strain (±6%) with a resolution of ~132 micro-strain (0.013%). In-tyre testing under static loading has shown the ability of the sensor to measure large tyre strains. The technology used for sensor fabrication lends itself to mass production and so the design is considered to be consistent with low cost commercialisable strain sensing technology.

This study presents a wearable system that mainly consisted of piezoelectric sensors, filter circuit and data logger in order to measure the vertical ground reaction force (VGRF) and study its profile. The proposed system establishes base information to improve the portable gait analysis systems and make them easier in use also to be able to get more outdoor data. The experiments were done by a young healthy person without physical disabilities or nervous disorders and the experimental protocol was explained to the participant before the performing. The experiment involved the walking with self-selected speed along 15 meter track of paved ground. The system was set on (200 Hertz) sampling rate in order to achieve the required data resolution. The produced information was about the events of the gait cycle (Heel-Strike, Stance, Heel-Off and Swing) and their durations also for the VGRF profile of each step and stride which compared with the VGRF profile of force plate. The results of VGRF of sensorinsole system clarified a high similarity with the VGRF produced by force plate system. Despite the system having many features, there are some limitations which can be avoided after improving the system.

This study presents an investigation of the inner tire surface strain measurement by using piezoelectric polymer transducers adhered on the inner liner of the tire, acting as strain sensors in both conventional and dual-chamber tires. The piezoelectric elements generate electrical charges when strain is applied. The inner liner tire strain can be found from the generated charge. A wireless data logger was employed to measure and transmit the measured signals from the piezoelectric elements to a PC to store and display the readout signals in real time. The strain data can be used as a monitoring system to recognize tire-loading conditions (e.g., traction, braking, and cornering) in smart tire technology. Finite element simulations, using ABAQUS, were employed to estimate tire deformation patterns in both conventional and dual-chamber tires for pure rolling and steady-state cornering conditions for different inflation pressures to simulate on-road and off-road riding tire performances and to compare with the experimental results obtained from both the piezoelectric transducers and tire test rig.